This invention relates generally to insulative structures and relates, more particularly, to an evacuated insulation structure, such as a panel.
Evacuated insulation of the type with which this invention is concerned have been proposed for use as substitute insulation for foamed polymer materials commonly utilized in the walls and doors for enclosures of refrigeration and freezing equipment and insulative barriers enveloping portable insulated containers such as coolers and insulated bottles available under the trade designation Thermos.
By utilizing preselected powders as filler materials for such panels, the panels are provided with desirable insulation properties, and unlike some refrigeration insulation, do not release chlorofluorocarbons into the environment. U.S. Pat. No. 4,636,415 describes one evacuated structure containing powder in the form of precipitated silica, and U.S. Pat. No. 4,681,788 describes another evacuated structure containing a mixture of precipitated silica and fly ash. Precipitated silica is limited, however, in that it is relatively expensive and its thermal properties are less than optimum.
It is an object of the present invention to provide a new and improved powder-filled evacuated insulation structure of the aforedescribed class.
Another object of the present invention is to provide such a structure which utilizes powder which, when compared to precipitated silica, has superior thermal insulating characteristics over a broad temperature range and can be produced in bulk relatively economically.